Abstract

The annual suicide rate in South Korea is the highest among the developed countries. Paraquat is a highly lethal herbicide, commonly used in South Korea as a means for suicide. We have studied the effect of the 2011 paraquat prohibition on the national suicide rate and method of suicide in South Korea. We obtained the monthly suicide rate from 2005 to 2013 in South Korea. In our analyses, we adjusted for the effects of celebrity suicides, and economic, meteorological, and seasonal factors on suicide rate. We employed change point analysis to determine the effect of paraquat prohibition on suicide rate over time, and the results were verified by structural change analysis, an alternative statistical method. After the paraquat prohibition period in South Korea, there was a significant reduction in the total suicide rate and suicide rate by poisoning with herbicides or fungicides in all age groups and in both genders. The estimated suicide rates during this period decreased by 10.0% and 46.1% for total suicides and suicides by poisoning of herbicides or fungicides, respectively. In addition, method substitution effect of paraquat prohibition was found in suicide by poisoning by carbon monoxide, which did not exceed the reduction in the suicide rate of poisoning with herbicides or fungicides. In South Korea, paraquat prohibition led to a lower rate of suicide by paraquat poisoning, as well as a reduction in the overall suicide rate. Paraquat prohibition should be considered as a national suicide prevention strategy in developing and developed countries alongside careful observation for method substitution effects.

The Y-axis represents monthly suicide rate per 10 million people. The black line indicates the trend of seasonal adjusted suicide rate. The gray horizontal line indicates the estimated values of suicide rate by the change point analysis. Two vertical lines indicate the prohibition dates (boundary line for production prohibition and dashed line for distribution prohibition). (A) Total suicides. (B) Suicide by poisoning with herbicides or fungicides. (C) Suicide by hanging. (D) Suicide by falling/jumping. (E) Suicide by other poisoning. (F) Suicide by any other method.

Change point analyses for method substitution effect by year in South Korea.

(A) Suicide by poisoning with other agricultural chemicals. (B) Suicide by poisoning with carbon monoxide. (C) Suicide by poisoning with any other substance. The Y-axis represents monthly suicide rate per 10 million people. The black line indicates the trend of seasonal adjusted suicide rate. The gray horizontal line indicates the estimated values of suicide rate by the change point analysis. Two vertical lines indicate the prohibition dates (boundary line for production prohibition and dashed line for distribution prohibition).